A new energy distribution network island detection method and system

Abstract

This invention discloses a method and system for detecting islanding in a new energy distribution network, belonging to the field of new energy grid connection technology. The method includes: collecting a reference value of active power at the rated frequency; sequentially performing frequency ramp-up to a first target frequency, frequency ramp-down to collect active power detection values, low-frequency reset of the power angle, and return to the rated frequency; and identifying the islanding state based on the ratio of [value missing]. The system includes modules for frequency control, data acquisition, judgment, and protection. This invention uses a small-amplitude frequency adjustment of ±0.1Hz, with each stage lasting 0.1s and a total detection cycle of 0.3s. It achieves discrimination by the difference in active power response between grid-connected and islanded states, has no detection blind spots, minimal impact on power quality, is simple to implement, and low in cost, making it suitable for grid-connected scenarios of photovoltaic, wind power, and other new energy inverters.

Description

Technical Field

[0001] This invention belongs to the field of new energy power generation grid connection technology, specifically relating to a method and system for detecting islanding in a new energy distribution network. Background Technology

[0002] With the increasing penetration of new energy sources such as photovoltaics and wind power in distribution networks, and the widespread grid connection of power electronic inverters, islanding has become a typical fault problem threatening the safe and stable operation of distribution networks. Islanding refers to the situation where, after a fault, maintenance, or switch disconnection in the distribution network, the new energy power generation system fails to detect its disconnection from the main grid in a timely manner and continues to supply power to local loads, forming an isolated power supply island. Islanding operation directly causes the voltage and frequency at the grid connection point to deviate from the rated range, leading to power quality deterioration and damage to precision electrical equipment. Furthermore, energized islanding operation poses a serious risk of electric shock to grid maintenance personnel. Therefore, rapid and reliable islanding detection is a core protection function that new energy grid connection must possess.

[0003] Currently, mainstream islanding detection methods are mainly divided into two categories: passive detection and active detection. Passive methods identify islanding by real-time monitoring of abrupt changes in electrical quantities such as voltage amplitude, frequency, phase, and harmonic content at the grid connection point. This does not require injecting disturbances into the grid and has no impact on power quality. However, this method has a fatal flaw: when the power generation of new energy sources is close to balanced with the local load power, parameters such as voltage and frequency will not show significant abnormal fluctuations, creating a power matching detection blind zone. This easily leads to islanding detection failure and cannot meet the requirements for high-reliability grid connection.

[0004] Active detection methods apply frequency disturbances, reactive power disturbances, and harmonic disturbances to the power grid, utilizing the differences in system response characteristics between grid-connected and islanded states to achieve detection, effectively reducing the detection blind zone. However, existing active detection methods still face many insurmountable technical challenges: Traditional active frequency shifting methods use continuous positive or negative frequency shifts, which can easily cause the grid frequency to deviate from the rated value for a long time, significantly reducing the power supply quality. When multiple machines are connected in parallel, disturbances may cancel each other out, leading to detection failure. The reactive power disturbance method achieves discrimination by injecting reactive power to change the system impedance. However, it is prone to misjudgment and has poor stability in scenarios such as unbalanced distribution networks, load fluctuations, and uneven line impedance. Some methods rely on complex signal processing algorithms such as wavelet decomposition, negative order components, and model identification, which have high computational cost, poor real-time performance, and high hardware implementation cost, making them difficult to widely apply in small and medium power new energy inverters. Existing methods generally suffer from problems such as slow detection speed, large disturbance amplitude, and poor adaptability to multi-machine grid connection. They cannot simultaneously ensure detection reliability, response speed, and power quality assurance, and are difficult to adapt to the operation requirements of distribution networks with a high proportion of new energy access.

[0005] In summary, existing islanding detection technologies cannot simultaneously meet the comprehensive requirements of no detection blind spots, low power quality impact, rapid response, simple implementation, multi-machine adaptability, and low cost, severely restricting the safety and large-scale application of renewable energy grid-connected systems. Therefore, it is urgent to propose a novel islanding detection method to break through the existing technical bottlenecks in principle and solve the above-mentioned technical problems. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method and system for detecting islanding in new energy distribution networks. By combining small-amplitude frequency adjustment with active power response characteristic analysis, it achieves rapid and accurate detection of islanding conditions, and the detection process has minimal impact on the power quality of the distribution network. This invention solves the technical problems of traditional islanding detection methods, such as large detection blind spots, significant impact on power quality, slow response speed, poor adaptability to multi-machine grid connection, and high hardware implementation costs. The method is simple to implement and is applicable to scenarios where new energy sources such as photovoltaic and wind power are connected to the distribution network through power electronic inverters.

[0007] The present invention adopts the following technical solution: A method for detecting islanding in a new energy distribution network includes the following steps: S1. When the inverter is running stably and connected to the grid, maintain the inverter output frequency at the rated frequency of the distribution network, and collect and record the reference value of the active power output of the inverter. ; S2. Start the islanding detection process and control the inverter output frequency to increase from the rated frequency to the first target frequency, where the first target frequency is higher than the rated frequency. S3. Once the inverter output frequency stabilizes at the first target frequency, control the inverter output frequency to drop back to the rated frequency of the distribution network. During the frequency drop-back process, collect and record the active power detection value of the inverter output. ; S4. Control the inverter output frequency to drop from the rated frequency to the second target frequency. The second target frequency is lower than the rated frequency, thus completing the power angle reset adjustment. S5. Control the inverter output frequency to rise from the second target frequency back to the rated frequency of the distribution network; S6. Based on the aforementioned active power reference value and the active power detection value Establish islanding criteria to identify whether the inverter is in islanded operation.

[0008] Preferably, in step S1, the rated frequency of the distribution network is 50Hz; the active power data output by the inverter is collected in real time by the detection module at the grid connection point, and a stable active power reference value is obtained after filtering and noise reduction processing. .

[0009] Preferably, in step S2, the first target frequency f1 is 50.1Hz; the duration for controlling the inverter output frequency to increase from the rated frequency to the first target frequency is 0.1s.

[0010] Preferably, in step S3, the duration for the inverter output frequency to drop from the first target frequency back to the rated frequency of the distribution network is 0.1s; during the frequency drop-off process, the active power data output by the inverter during this stage is collected in real time and continuously by the grid connection point detection module, and a stable active power detection value is obtained after data processing. .

[0011] Preferably, in step S4, the second target frequency f2 is 49.9Hz; the duration for controlling the inverter output frequency to drop from the rated frequency to the second target frequency is 0.1s; after the frequency drops, the inverter's power angle decreases synchronously with the decrease in output frequency, and the power angle recovers to the initial normal operating power angle value.

[0012] Preferably, in step S5, after the inverter output frequency reaches the second target frequency and the power angle is reset, the inverter output frequency is controlled to rise from the second target frequency back to the rated frequency of the distribution network, thus ending the frequency adjustment process of the entire islanding detection.

[0013] Preferably, in step S6, the islanding state criterion is: , This is the reliability coefficient.

[0014] Preferably, the reliability coefficient The value is 1.2.

[0015] Preferably, when At that time, it is determined that the inverter is still in normal grid-connected operation. when When the inverter enters islanded operation mode, the inverter's disconnection protection action is triggered.

[0016] Secondly, embodiments of the present invention provide a new energy distribution network islanding detection system, comprising: The frequency control module is used to maintain the inverter output frequency at the rated frequency of the distribution network when the inverter is running normally and stably connected to the grid, and to perform frequency regulation operations during the islanding detection process. The detection module, connected to the frequency control module, is used to acquire and record the reference value of the active power output by the inverter when the inverter output frequency is the rated frequency. And during the frequency fall-off process, the active power detection value of the inverter output is collected and recorded. ; The data module, connected to the detection module, is used to filter and denoise the collected active power data to obtain a stable active power reference value. and active power detection value ; The judgment module, connected to the data module, is used to determine the active power reference value. and active power detection value The islanding criterion is used to identify whether the inverter is in islanding operation. The execution module, connected to the judgment module, is used to trigger the inverter's disconnection protection action when it is determined that the inverter has entered the islanded operation state.

[0017] Thirdly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for detecting islanding in a new energy distribution network.

[0018] Fourthly, embodiments of the present invention provide a computer-readable storage medium including a computer program, which, when executed by a processor, implements the steps of the above-described method for detecting islanding in a new energy distribution network.

[0019] Fifthly, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for detecting islanding in a new energy distribution network.

[0020] Sixthly, embodiments of the present invention provide an electronic device including a computer program, which, when executed by the electronic device, implements the steps of the above-described method for detecting islanding in a new energy distribution network.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: A new energy distribution network islanding detection method employs a four-stage symmetrical adjustment strategy of frequency boosting-fallback acquisition-frequency reduction reset-rise, introducing only a tiny disturbance of ±0.1Hz within a very short time, far below the grid frequency deviation standard, achieving "zero-perception" impact on grid power quality. Simultaneously, by utilizing the strong coupling characteristics of power angle and active power in grid-connected mode and the essential difference between this coupling failure in islanded mode, a highly sensitive physical criterion is constructed. This method eliminates the need for reactive power or harmonic injection, avoids mutual interference when multiple inverters are connected in parallel, significantly reduces the detection blind zone, and features simple logic, making it easy to embed in low-cost inverter controllers.

[0022] Furthermore, by introducing filtering and noise reduction preprocessing, background harmonics from the power grid, measurement noise, and instantaneous power fluctuations caused by load fluctuations are effectively filtered out, ensuring the reference value. The purity of the data directly improves the signal-to-noise ratio of subsequent criterion calculations, prevents misjudgments caused by data fluctuations, and significantly enhances the robustness and reliability of the detection algorithm in complex electromagnetic environments.

[0023] Furthermore, an offset of 0.1 Hz is sufficient to induce a significant change in the power angle under grid-connected conditions, thereby generating an observable increase in active power. At the same time, it lies within the linear region of the frequency characteristics of most loads, avoiding the induction of nonlinear responses in the loads. The short duration of 0.1 s ensures the establishment of the system's dynamic response while minimizing the impact on the power grid, thus minimizing the impact on sensitive loads on the user side while maintaining detection sensitivity.

[0024] Furthermore, when the frequency drops from its high point to its rated value, if the system is connected to the grid, the power angle remains at a relatively large value, and the measured value at this time... It can maximize the reflection of the power gain caused by changes in the power angle; while in an islanded environment, the power remains constant and determined by the load. By selecting to collect data at the moment of stabilization after a drop-off, it avoids transient oscillation interference during drastic frequency changes and obtains the feature values ​​that best reflect the power angle-power mapping relationship, greatly improving the discrimination of the criteria and the accuracy of detection.

[0025] Furthermore, by using reverse symmetrical adjustment, the power angle is forcibly pulled back to the initial state, ensuring that the inverter immediately returns to the optimal operating point after the detection is completed, without affecting the subsequent MPPT efficiency or grid connection stability, thus completely eliminating the negative impact of active detection on the long-term operating performance of the system.

[0026] Furthermore, by providing clear recovery instructions, any residual frequency deviation risk is eliminated, ensuring that the inverter seamlessly transitions to normal grid-connected control mode after the detection cycle ends. This allows for high-frequency periodic execution, enabling real-time and continuous monitoring of islanding faults.

[0027] Furthermore, a reliability coefficient is introduced. k >1. A clear safety margin is established between theoretical islanding and grid connection. Simulation verification shows that... k =1.2 can effectively cover the uncertainties caused by measurement errors, communication delays and minor load fluctuations, which not only eliminates the omission of islanding detection, but also avoids false alarms during normal grid connection.

[0028] Furthermore, it operates silently under normal conditions and immediately disconnects from the grid when islanded, directly corresponding to the code implementation logic of the inverter control software. This ensures that the system can disconnect the electrical connection as quickly as possible when a dangerous condition is detected, preventing voltage runaway, frequency collapse, and electric shock risks to maintenance personnel caused by islanded operation.

[0029] It is understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0030] In summary, the method of this invention has a small detection blind zone, no power matching failure problem, and small-amplitude frequency disturbances have almost no impact on power quality. It has a fast detection response of 0.3s. The criteria are simple, the computation is small, the hardware cost is low, and it is suitable for small and medium power inverters and multi-machine grid connection. It has strong anti-interference and low false judgment rate, and combines detection accuracy, safety and engineering practicality. It is comprehensively superior to traditional passive and active islanding detection methods.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] Figure 1 This is a typical topology for a new energy grid-connected system; Figure 2 This is a flowchart of the detection method of the present invention; Figure 3 A model diagram of a distribution network system with a high proportion of renewable energy access; Figure 4 shows the waveform diagram of the inverter in grid-connected operation, where (a) is the three-phase voltage and current waveform, and (b) is the active and reactive power waveform. Figure 5 shows the waveform diagram of the inverter operating off-grid, where (a) is the three-phase voltage and current waveform, and (b) is the active and reactive power waveform. Figure 6 A schematic diagram of a computer device provided in an embodiment of the present invention; Figure 7 This is a block diagram of a chip provided according to an embodiment of the present invention.

[0033] Among them, 60. Computer equipment; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access memory unit; 6202. Cache memory unit; 6203. Read-only memory unit; 6204. Program / utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0036] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0037] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0038] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0039] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0040] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0041] This invention provides a method for detecting islanding in a new energy distribution network. It is applied to the grid connection point where a new energy power generation system connects to the distribution network. The new energy power generation system operates in grid-connected mode via a power electronic inverter. Based on the strong correlation between active power and power angle in a multi-machine parallel system, islanding detection is achieved by utilizing the different effects of power angle adjustment on the inverter's output active power under grid-connected and islanded conditions: When the inverter is operating in grid-connected mode, an increase in power angle will significantly increase the inverter's output active power; when the inverter is disconnected from the distribution network and enters islanded operation, the effect of increasing power angle on the inverter's output active power is almost ineffective, and the active power remains basically stable. Therefore, the grid-connected operation status of the inverter can be accurately determined.

[0042] Please see Figure 1 In a typical topology of a renewable energy grid-connected system, the inverter operates at the same frequency as the system side during normal operation, supplying active power to the system. Assume the system-side voltage is... The inverter-side voltage is The current injected into the system by the inverter is: (1) Among them, X ∑ This is the equivalent impedance of the system.

[0043] From Euler's formula, we can obtain: (2) Lianlide: (3) in, , The active and reactive currents injected into the system by the inverter.

[0044] The active power injected into the system by the inverter is: (4) Please see Figure 2 The present invention provides a method for detecting islanding in a new energy distribution network, comprising the following steps: S1. When the inverter is running normally and stably connected to the grid, the frequency control module maintains the inverter output frequency at the distribution network rated frequency of 50Hz. At this time, the system is in a stable power balance operation state. The active power data output by the inverter is collected in real time by the detection module at the grid connection point. After filtering and noise reduction processing, a stable active power reference value is recorded. ; Let the power angle of the inverter under normal operating conditions be δ0. The active power delivered by the inverter to the system at this time is determined by equation (4): (5) S2. Start the islanding detection process and issue a frequency adjustment command through the inverter's frequency control module to control the inverter's output frequency to increase from the rated 50Hz to the target frequency f1=50.1Hz; The duration of this frequency boost phase is precisely set to 0.1 seconds.

[0045] S3. Once the inverter output frequency reaches and stabilizes at the target frequency f1, a frequency reduction command is issued through the frequency control module to lower the inverter output frequency from 50.1Hz to the rated frequency of the distribution network, 50Hz. The duration of this frequency reduction phase is also set to 0.1s. During the frequency reduction process, the active power data output by the inverter is continuously collected in real time by the grid connection point detection module, and the stable active power detection value is recorded after data processing. ; During this stage, the inverter's power angle stabilizes at δ1 (δ1>δ0). According to equation (4), the active power output by the inverter at this time is: (6) S4, Active power detection value After the data acquisition is completed, the inverter's frequency control module continues to output frequency adjustment commands to reduce the inverter's output frequency from the rated 50Hz to the target frequency f2=49.9Hz. The duration of this frequency reduction phase is still 0.1s. After the frequency decreases, the inverter's power angle will decrease synchronously with the decrease in output frequency, and the power angle will return to the initial normal operating value δ0, completing the power angle reset adjustment. S5. When the inverter output frequency reaches the target frequency f2 and the power angle is reset to δ0, the frequency control module issues a frequency increase command to raise the inverter output frequency from 49.9Hz to the distribution network rated frequency of 50Hz. At this point, the frequency adjustment process of the entire islanding test ends, and the inverter returns to the normal grid-connected frequency and power angle operation state, waiting for the start of the next islanding test process. S6. Based on the essential differences in system operating characteristics under grid-connected and islanded states, establish a mathematical model for active power comparison and judgment and islanded state criteria to achieve accurate identification of islanded state.

[0046] To maintain stable grid-connected operation of the inverter, both the inverter power angles δ0 and δ1 are less than 90°. Based on the system support characteristics analysis of grid-connected and islanded states: if the inverter is not disconnected from the grid during islanding detection and remains in normal grid-connected state, the main grid provides stable frequency and voltage support to the system. The increase in power angle due to frequency regulation (δ1>δ0) will directly lead to a significant increase in the inverter's output active power. Clearly, this has… > If the inverter has disconnected from the grid and entered islanded operation during islanding detection, the inverter loses grid support and becomes the frequency and voltage source for the local islanded system. Frequency regulation cannot change the system's active power balance, and power angle changes cannot affect active power output. Therefore, = Therefore, the following criteria can be used to determine whether an inverter has entered islanded operation mode: (7) Where k is the reliability coefficient, and its value is greater than 1. After multiple verifications by Matlab / Simulink electromagnetic transient simulations, it was found that when k is 1.2, it can effectively reduce the probability of false detection while ensuring detection reliability and avoiding missed detection, which is the optimal value.

[0047] When the detection result meets the criterion, it is determined that the inverter has entered the islanded operation state, and the inverter's disconnection protection action is immediately triggered. If the test result does not meet the criterion, the inverter is determined to be still in normal grid-connected operation and the inverter maintains its original grid-connected operating conditions.

[0048] The detection methods of this invention are simple and easy to implement, requiring no complex signal processing and logic operations. They can be directly embedded into the frequency control module of a new energy inverter, adapting to the hardware implementation requirements of small and medium power new energy inverters, and can complete a complete islanding detection process in a very short time.

[0049] In another embodiment of the present invention, a new energy distribution network islanding detection system is provided. This system can be used to implement the above-mentioned new energy distribution network islanding detection method. Specifically, the new energy distribution network islanding detection system includes a frequency control module, a detection module, a data module, a judgment module, and an execution module.

[0050] Among them, the frequency control module is used to maintain the inverter output frequency at the rated frequency of the distribution network when the inverter is running normally and stably connected to the grid, and to perform frequency adjustment operations in the islanding detection process. The detection module, connected to the frequency control module, is used to acquire and record the reference value of the active power output by the inverter when the inverter output frequency is the rated frequency. And during the frequency fall-off process, the active power detection value of the inverter output is collected and recorded. ; The data module, connected to the detection module, is used to filter and denoise the collected active power data to obtain a stable active power reference value. and active power detection value ; The judgment module, connected to the data module, is used to determine the active power reference value. and active power detection value The islanding criterion is used to identify whether the inverter is in islanding operation. The execution module, connected to the judgment module, is used to trigger the inverter's disconnection protection action when it is determined that the inverter has entered the islanded operation state.

[0051] This invention provides a terminal device comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or function. The processor described in this embodiment can be used in the operation of a new energy distribution network islanding detection method, including: During normal grid-connected and stable operation of the inverter, maintain the inverter output frequency at the rated frequency of the distribution network, and collect and record the baseline value of the active power output of the inverter. The islanding detection process is initiated, controlling the inverter output frequency to increase from the rated frequency to a first target frequency, which is higher than the rated frequency. Once the inverter output frequency stabilizes at the first target frequency, the inverter output frequency is controlled to drop back to the rated frequency of the distribution network. During the frequency drop-off process, the active power output value of the inverter is collected and recorded. The inverter output frequency is controlled to decrease from the rated frequency to the second target frequency, which is lower than the rated frequency, thus completing the power angle reset adjustment; the inverter output frequency is controlled to increase from the second target frequency back to the rated frequency of the distribution network; based on the active power reference value... and the active power detection value Establish islanding criteria to identify whether the inverter is in islanded operation.

[0052] Please see Figure 6The terminal device is a computer device. In this embodiment, the computer device 60 includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the processor 61 executes the computer program 63, it implements the islanding detection method for the new energy distribution network in this embodiment. To avoid repetition, these details are not elaborated here. Alternatively, when the processor 61 executes the computer program 63, it implements the functions of each model / unit in the new energy distribution network islanding detection system of this embodiment. To avoid repetition, these details are not elaborated here.

[0053] Computer device 60 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. Computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will understand that... Figure 6 This is merely an example of computer device 60 and does not constitute a limitation on computer device 60. It may include more or fewer components than shown, or combine certain components, or different components. For example, computer device may also include input / output devices, network access devices, buses, etc.

[0054] The processor 61 may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0055] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc. equipped on the computer device 60.

[0056] Furthermore, the memory 62 may include both internal storage units of the computer device 60 and external storage devices. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0057] Please see Figure 7 The terminal device is an electronic device 600, which is manifested in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including storage unit 620 and processing unit 610), a display unit 640, etc.

[0058] The storage unit stores program code, which can be executed by the processing unit 610 to perform the steps described in the method section of this specification according to various exemplary embodiments of the present invention. For example, the processing unit 610 can perform actions such as... Figure 2 The steps are shown in the figure.

[0059] Storage unit 620 may include a readable medium in the form of a volatile storage unit, such as random access memory (RAM) 6201 and / or cache memory 6202, and may further include a read-only memory (ROM) 6203.

[0060] Storage unit 620 may also include a program / utility 6204 having a set (at least one) program module 6205, such program module 6205 including but not limited to: operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0061] Bus 630 can represent one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of the multiple bus structures.

[0062] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem). This communication can be performed via input / output interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network, wide area network, and / or public network, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0063] Example 4 This invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It is understood that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device; it can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor, which can be one or more computer programs (including program code). More specific examples of the computer-readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical fiber, portable compact disk read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0064] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium can also be any readable medium other than a readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, radio frequency, etc., or any suitable combination thereof.

[0065] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0066] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the islanding detection method for new energy distribution networks in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor in the following steps: During normal grid-connected and stable operation of the inverter, maintain the inverter output frequency at the rated frequency of the distribution network, and collect and record the baseline value of the active power output of the inverter. The islanding detection process is initiated, controlling the inverter output frequency to increase from the rated frequency to a first target frequency, which is higher than the rated frequency. Once the inverter output frequency stabilizes at the first target frequency, the inverter output frequency is controlled to drop back to the rated frequency of the distribution network. During the frequency drop-off process, the active power output value of the inverter is collected and recorded. The inverter output frequency is controlled to decrease from the rated frequency to the second target frequency, which is lower than the rated frequency, thus completing the power angle reset adjustment; the inverter output frequency is controlled to increase from the second target frequency back to the rated frequency of the distribution network; based on the active power reference value... and the active power detection value Establish islanding criteria to identify whether the inverter is in islanded operation.

[0067] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0069] Detection process under different load characteristics To further illustrate the effectiveness of the present invention under different load scenarios, this embodiment combines... Figure 3 The power distribution network model shown describes the detection process under two typical load conditions in detail.

[0070] Operating Condition A: Resistive load-dominant scenario (RL load) In this scenario, the local load mainly consists of resistors and inductors. When step S2 is executed to increase the frequency from 50Hz to 50.1Hz, since the load impedance increases slightly with frequency, if the system is in islanded mode, the inverter output voltage needs to be adjusted to maintain power balance. However, due to the inverter control strategy, its output active power is limited. P The basic level remains constant (determined by the load), i.e. ≈ .

[0071] Conversely, if it is in grid-connected state, the main grid voltage Ug A constant frequency increase causes the inverter output voltage phase to lead, resulting in a power angle... δ Increase. According to the formula. Active power P Follow δ The frequency increases significantly. At the instant in step S3 when the frequency drops back to 50Hz but the power angle remains at δ1, the collected data... Will be significantly greater than (Simulation shows an increase of over 20%). Criterion at this point. >1.2 The system was established and determined to be connected to the grid. Subsequently, step S4 was executed to downclock the frequency to 49.9Hz, and the power angle... δ Decrease and reset to δ0 to ensure the system is unbiased.

[0072] Operating Condition B: Capacitive or resonant load scenarios (high-risk blind spot) Traditional AFD methods are prone to failure when the load resonant frequency coincides with the disturbance frequency. In this embodiment, it is assumed that the local load is an RLC parallel resonant circuit with a resonant frequency close to 50Hz.

[0073] When steps S2 to S3 of this invention are executed, even if the load exhibits capacitive behavior or resonance, because the detection basis is the rate of change of active power rather than the direction of frequency drift, in islanded mode the inverter loses the support of the main grid. Although its output frequency is forcibly adjusted, its output power is strictly limited by the consumption capacity of the local load. Therefore, Unable to surpass .

[0074] In grid-connected mode, regardless of load characteristics, as long as the main grid exists, changes in the power angle will inevitably cause changes in transmission power (unless the power angle is 0 or 90 degrees, but the normal operating point is between 0-30 degrees, where sensitivity is highest). Therefore, even under high Q-value loads, and The difference remains significant, criterion >1.2 It still operates reliably, completely eliminating the resonance dead zone.

[0075] Collaborative detection in multi-machine parallel scenarios In power distribution stations with a high proportion of renewable energy integration, multiple inverters often operate in parallel. This embodiment illustrates the application of the present invention in a multi-inverter scenario.

[0076] Assume there are N inverters in the station, all loaded with the algorithm described in this patent. Since the detection period of each inverter can be set to random peak shifting (e.g., random start within 0-1 seconds), or even if they start synchronously, the superposition effect caused by the simultaneous disturbance of multiple devices is far less than the grid frequency tolerance threshold because the disturbance amplitude used in this invention is extremely small (±0.1Hz) and the time is extremely short (0.1s).

[0077] More importantly, this method does not rely on positive feedback mechanisms (i.e., it does not require the continuous accumulation of frequency deviations), thus eliminating frequency conflicts or system instability caused by differences in positive feedback gain between multiple inverters. Each inverter operates independently based on its own... and The system makes judgments without interfering with each other. If one inverter detects islanding (e.g., the main grid is disconnected), it is quickly disconnected. The remaining inverters, having lost the support of the main grid, will also be immediately determined to be islanded in the next detection cycle and disconnected in sequence. This achieves rapid interlocking protection for the multi-unit system and avoids the risk of the remaining units continuing to operate in islanded mode after a single unit is disconnected.

[0078] The specific logic flow of hardware implementation This embodiment provides a specific code implementation logic based on a DSP controller.

[0079] Timer interrupt settings: Set a high-precision timer interrupt in the DSP with a period of 10ms.

[0080] State machine design: Establish IDLE (idle) and UP (upper) states. FREQ (Upclocking), DOWN MEASURE (Loss measurement), RESET FREQ It has five states: (Reset), RECOVER, etc.

[0081] Data Acquisition: In IDLE mode, active power is calculated and filtered using a moving average method for each power cycle, and then updated. .

[0082] Disturbance execution: When the detection flag is triggered, enter UP. FREQ Modify the PLL (phase-locked loop) reference frequency register to 50.1Hz and count 10 cycles (0.1s).

[0083] Key sampling: Switch to DOWN MEASURE The reference frequency is changed back to 50Hz, but the current power calculation result is locked as the reference frequency during the 5th-10th cycles after the switch. This step requires disabling the conventional power loop integrator to prevent it from rapidly tracking and causing... It was dragged down.

[0084] Reset and Judgment: Enter RESET FREQ The reference frequency was set to 49.9Hz for 0.1s, forcing the power angle to decrease; then it entered RECOVER mode to restore 50Hz. Comparison was performed in the interrupted background task. Compared with 1.2 If the condition is met, set the Island flag. Flag This triggers the GPIO pin to output a trip signal.

[0085] Simulation verification To fully verify the correctness, reliability, and practicality of the proposed islanding detection method for renewable energy distribution networks based on frequency regulation and active power response in high-proportion renewable energy integration distribution networks, this simulation uses the SimPowerSystems toolbox in Matlab / Simulink to build an electromagnetic transient simulation model, with a simulation step size set to 1e. -5 The simulation duration is set to 0.3 seconds to ensure accurate capture of details related to changes in electrical quantities. This covers the entire frequency regulation phase and the active power acquisition and comparison cycle. The model parameters are as follows: Positive sequence resistance: 0.03206Ω / km; Positive sequence reactance: 0.36Ω / km; Positive sequence susceptance: 3.7 × 10⁻⁶ 6S / km; Zero-sequence resistance: 0.096Ω / km; Zero-sequence reactance: 1.5Ω / km; Zero-sequence susceptance: 3 × 10 6S / km; The lengths of L1, L2, and L3 are 10km, 10km, and 5km, respectively.

[0086] This simulation focuses on collecting and analyzing two core data points: the three-phase voltage and current waveforms at the grid connection point, and the instantaneous active / reactive power waveforms at the inverter output. By comparing the data change characteristics under two scenarios, the effectiveness of the detection method of this invention is verified.

[0087] (I) Scenario 1: Simulation results of inverter operating normally in grid connection In grid-connected mode, the inverter is supported by the frequency and voltage of the main distribution network. Frequency regulation directly changes the inverter's power angle, thus affecting the output active power. The core simulation results are as follows: Three-phase voltage and current: During the frequency regulation phase of 0.2~0.3s, the three-phase voltage at the grid connection point remains stable at the rated value (without significant amplitude or phase fluctuations), the amplitude of the three-phase current increases significantly, and the waveform of the three-phase current remains sinusoidal with no significant harmonic distortion, indicating that the small-amplitude frequency regulation (±0.1Hz) of the present invention has no negative impact on the power quality of the power grid, as shown in Figure 4(a). Active / Reactive Power: In the initial stage (0~0.2s), the active power P0 remains stable. From 0.3 to 0.4s, when the frequency drops back to 50Hz and the power angle remains at δ1, the active power P1 shows a significant jump compared to P0. The reactive power remains basically stable throughout the process, indicating that the increase in power angle is the only core factor for the increase in active power. Moreover, under grid-connected conditions, the rule of P1>1.2P0 is satisfied. The criterion determines that it is a non-islanded state, with no misjudgment, as shown in Figure 4(b).

[0088] (II) Scenario 2: Simulation results of inverter islanding and grid disconnection operation In islanded mode, the inverter loses the support of the main distribution network and becomes the frequency and voltage source of the local islanded system. Frequency regulation cannot change the active power balance of the system. The core simulation results are as follows: Three-phase voltage and current: During the entire frequency regulation phase, the amplitude and phase of the three-phase voltage and current at the grid connection point did not change significantly, and the current waveform remained stable, indicating that the power balance of the islanded system was not broken by the small-amplitude frequency regulation, and the system operation was stable, as shown in Figure 5(a). Active / Reactive Power: The initial active power P0 remains stable. During the 0.3~0.4s acquisition phase, the active power P1 is basically the same as P0, and the reactive power does not fluctuate significantly. This indicates that the change in the power angle under islanded state cannot change the active power output of the inverter, satisfying the rule P1=P0<1.2P0. The criterion accurately determines that it is in islanded state, as shown in Figure 5(b).

[0089] Simulation results show that this method can accurately distinguish between grid-connected and islanded states by the characteristics of active power change. It only uses a small frequency adjustment of ±0.1Hz, which is lower than the allowable deviation standard of grid frequency. Moreover, there is no obvious harmonic distortion of voltage and current during the detection process, and the impact on the power quality of the distribution network is minimal, which has certain practical value.

[0090] In summary, this invention provides a method and system for detecting islanding in a new energy distribution network. By combining small-amplitude frequency adjustment with active power response discrimination, it comprehensively solves the shortcomings of traditional islanding detection from both the principle and implementation levels, achieving significant technical benefits. It completely eliminates power matching blind spots, accurately identifying islanding based on power response differences regardless of whether the new energy output and load are balanced, with a detection accuracy approaching 100%. Employing an extremely small disturbance of ±0.1Hz, far below the allowable deviation of the grid frequency, the detection process is free of harmonic distortion and voltage fluctuations, having no negative impact on the power quality of the distribution network, far superior to traditional active frequency shifting and reactive power disturbance methods. The total detection cycle is only 0.3s, with a fast response speed, enabling timely triggering of disconnection protection to avoid equipment damage and personal safety risks. The detection logic is simple, requiring no complex algorithms such as wavelet decomposition and negative sequence analysis, resulting in low computational load. It can be directly embedded into conventional inverter controllers, resulting in low hardware costs and adaptability to small to medium power scenarios. It has strong anti-interference capabilities; after filtering and noise reduction, it can adapt to complex operating conditions such as distribution network imbalance and load fluctuations, and exhibits excellent adaptability to multi-unit grid connection. The system achieves a unified approach that combines high precision, fast response, low disturbance, low cost, and high adaptability, significantly improving the safety and stability of new energy grid-connected systems and possessing extremely high engineering application value.

[0091] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0092] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0093] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0094] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0095] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0096] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0097] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random-access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0098] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0099] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0100] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0101] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for detecting islanding in a new energy distribution network, characterized in that, Includes the following steps: S1. When the inverter is running stably and connected to the grid, maintain the inverter output frequency at the rated frequency of the distribution network, and collect and record the reference value of the active power output of the inverter. ; S2. Start the islanding detection process and control the inverter output frequency to increase from the rated frequency to the first target frequency, where the first target frequency is higher than the rated frequency. S3. Once the inverter output frequency stabilizes at the first target frequency, control the inverter output frequency to drop back to the rated frequency of the distribution network. During the frequency drop-back process, collect and record the active power detection value of the inverter output. ; S4. Control the inverter output frequency to drop from the rated frequency to the second target frequency. The second target frequency is lower than the rated frequency, thus completing the power angle reset adjustment. S5. Control the inverter output frequency to rise from the second target frequency back to the rated frequency of the distribution network; S6. Based on the aforementioned active power reference value and the active power detection value Establish islanding criteria to identify whether the inverter is in islanded operation.

2. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S1, the rated frequency of the distribution network is 50Hz; the active power data output by the inverter is collected in real time by the detection module at the grid connection point, and a stable active power reference value is obtained after filtering and noise reduction. .

3. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S2, the first target frequency f1 is 50.1Hz; the duration for controlling the inverter output frequency to increase from the rated frequency to the first target frequency is 0.1s.

4. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S3, the duration for the inverter output frequency to drop from the first target frequency back to the rated frequency of the distribution network is 0.1s. During the frequency drop-off process, the active power data output by the inverter during this stage is collected in real time and continuously by the grid connection point detection module, and a stable active power detection value is obtained after data processing. .

5. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S4, the second target frequency f2 is 49.9Hz; the duration for the inverter output frequency to drop from the rated frequency to the second target frequency is 0.1s; after the frequency drops, the inverter's power angle decreases synchronously with the decrease in output frequency, and the power angle recovers to the initial normal operating power angle value.

6. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S5, after the inverter output frequency reaches the second target frequency and the power angle is reset, the inverter output frequency is controlled to rise from the second target frequency back to the rated frequency of the distribution network, thus ending the frequency adjustment process of the entire islanding detection.

7. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, In step S6, the islanding state criterion is: , This is the reliability coefficient.

8. The method for detecting islanding in a new energy distribution network according to claim 7, characterized in that, The reliability coefficient The value is 1.

2.

9. The method for detecting islanding in a new energy distribution network according to claim 1, characterized in that, when At that time, it is determined that the inverter is still in normal grid-connected operation. when When the inverter enters islanded operation mode, the inverter's disconnection protection action is triggered.

10. A new energy distribution network islanding detection system, characterized in that, include: The frequency control module is used to maintain the inverter output frequency at the rated frequency of the distribution network when the inverter is running normally and stably connected to the grid, and to perform frequency regulation operations during the islanding detection process. The detection module, connected to the frequency control module, is used to acquire and record the reference value of the active power output by the inverter when the inverter output frequency is the rated frequency. And during the frequency fall-off process, the active power detection value of the inverter output is collected and recorded. ; The data module, connected to the detection module, is used to filter and denoise the collected active power data to obtain a stable active power reference value. and active power detection value ; The judgment module, connected to the data module, is used to determine the active power reference value. and active power detection value The islanding criterion is used to identify whether the inverter is in islanding operation. The execution module, connected to the judgment module, is used to trigger the inverter's disconnection protection action when it is determined that the inverter has entered the islanded operation state.

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